python - Pygame, trying to erase sprite -

i making pygame app

with app, can place blue dot around screen mouse right click.

middle mouse supposed erase dot, feature isn't working....

any idea ?

# -*- coding: utf-8 -*-  import pygame pygame.locals import *   def func_circle(x,y):     cercle=pygame.sprite.sprite()     pygame.sprite.sprite.__init__(cercle)     cercle.image=pygame.surface((500,500))     cercle.image.fill((0,0,0))     cercle.image.set_colorkey((0,0,0))     pygame.draw.circle(cercle.image,(0,0,255),(cercle.image.get_rect().centerx,cercle.image.get_rect().centery),25,0)     cercle.image.convert_alpha()     cercle.rect=cercle.image.get_rect()     cercle.rect.centerx=x     cercle.rect.centery=y         return cercle   pygame.init() fenetre = pygame.display.set_mode((640, 480))  background = pygame.surface(fenetre.get_size()) background = background.convert() background.fill((250, 250, 250))  liste_des_sprites = pygame.sprite.layeredupdates()  continuer = 1 while continuer:     event in pygame.event.get():         if event.type==mousebuttondown , event.button==3:                                     my_cicle=func_circle( event.pos[0],event.pos[1])                        liste_des_sprites.add(my_cicle)          if event.type==mousebuttondown , event.button==2:             print "trying erase blue dot"             my_cicle.kill()             liste_des_sprites.empty()          if event.type==quit:             continuer=0      liste_des_sprites.draw(fenetre)       pygame.display.update() 

you have clear screen - example fill black color

fenetre.fill( (0,0,0) ) # clear screen  liste_des_sprites.draw(fenetre) # draw circles again  pygame.display.update() # send screen on monitor 

or draw background remove old elements.

fenetre.blit( background, (0,0) ) # blit background clear screen  liste_des_sprites.draw(fenetre) # draw circles again  pygame.display.update() # send screen on monitor